Alkyl glyceryl ether sulfonates (AGES) are well known as detergents utilized in personal care cleansing products. Although much literature is present disclosing their use in compositions, there is not a substantial amount of published literature relating to their synthesis. For example a 1976 review article by David Whyte entitled Alkyl Glyceryl Ethers Sulfonates appearing in Surfactant Science Series, Vol. 7, Anionic Surfactants part 2 at pages 483-494 reviews methods of preparing AGES. However most of the citations reviewed are significantly older than the review article. Among the reviewed documents are two Whyte U.S. patents, U.S. Pat. Nos. 2,989,547 and 3,024,273. In these patents, several methods of making AGES are disclosed including a detailed continuous process complete with figures in U.S. Pat. No. 3,024,273. This patent discloses the conversion of the chlorohydrin to the alkyl glyceryl ether sulfonate by the Strecker reaction using sodium sulfite.
The recycled sulfonate product is used to promote emulsification of the reactants in the mixer so that the sulfonation reaction is readily maintained and the recycled sulfonate normally comprises about 5% by weight of the total amount of material fed into the system. Depending upon the concentration of sodium sulfite, the undried sulfonation product will contain at least 50% water. Reaction contact time is from 4 to 20 minutes but reactant flow and reactor size are normally scaled so that reactor residence time is about ten minutes.
In U.S. Pat. No. 2,989,547 the glycidyl ether intermediate is disclosed as sulfonated to the alkyl glyceryl ether sulfonate using a mixture of sodium sulfite and bisulfite. The process can be carried out in a continuous manner. This sulfonation reaction can be carried out at moisture levels of well below 50% and even as low as about 30%. Using a 10% "paste seed" of alkyl glyceryl ether sulfonate, the batch reaction will initially proceed at temperatures as low as 300.degree. F.
With respect to these disclosures in the above two U.S. patents, several cautionary statements are made in the aforementioned Whyte review article. For example at page 490, Whyte states that solids contents of greater than 60% can be achieved in glycidyl ether sulfonation but difficulties in temperature control and excessive product viscosities make it undesirable to achieve these higher solids levels.
Methods of making alkoxylated alkyl glyceryl ether sulfonates are disclosed in Wellington et al, U.S. Pat. No. 4,502,538 and Gaertner U.S. Pat. No. 3,228,979. In Wellington, the corresponding glycidyl ether (epoxide) is converted to the sulfonate by reacting with aqueous sodium bisulfite or first reacting it with sodium hydroxide and then reacting it with the bisulfite. No temperatures are mentioned. Gaertner states than an alkali metal sulfite or bisulfite can be used to sulfonate the corresponding ether while preferably neutralizing the hydroxide as it is formed in the reaction by adding acid to a pH of 6-8 and definitely below 10 when using preferred solvents. The reaction is conducted in the presence of a diluent or solvent such as water or an organic solvent. Although water can be used without admixture with one of the other solvents, it is usually preferred to admix the water with ethanol in approximately equal amounts for use as a solvent. The use of water as a solvent without admixture with ethanol requires a higher temperature and generally requires the use of elevated pressure. When using a water ethanol-solvent, the temperature of reaction is from 50.degree.-120.degree. C. If no ethanol is used the same temperature range can be employed, however a reaction time of 2-3 days will be required. If a reaction temperature of 190.degree. C. is used without ethanol the reaction time will be 1 to 2 hours. With respect to times and temperatures of the specific examples, the first six specific examples utilizing water and ethanol as the cosolvents and a temperature 80.degree.-83.degree. C. were from 43/4 to 25 hours. In examples 7-9 only water was used and a pressure bomb was used as the reactor. A temperature range of 175.degree. to 195.degree. C. brought a reaction time of 13/4 to 2 hours. There is no mention of continuous processes in either reference and all the Gaertner examples are batch processes.
A new process for preparing alkoxylated alkyl glyceryl ether sulfonates has now been discovered. This process is continuous with a short reactor time and utilizes high contact quantities of sulfonated product together with the reactants, while achieving unusually high solids content of sulfonated product with accompanying low moisture levels. The reaction temperature is readily controllable at least in part because of the surprisingly low viscosity of the reactor contents at high solids content of sulfonated product, thereby also allowing for easy handling at all stages of the continuous process.